I. Liners
The subject matter of the present disclosure is applicable to a classification of products known in the relevant industry as “liners.” Conventional liners are coverings used to protect a surface from wear, corrosive materials, adhering materials, or the like. Such liners can be used in any of a variety of commercial, industrial, and residential applications. Examples may include lining various material handling or transportation equipment surfaces, such as vehicle beds and tanks; railroad car beds and tanks; decks; construction equipment, such as buckets, conveyors, scrapers, or the like; mining equipment, such as screening media, lip liners, tube covers, side rails, and chute liners; farm equipment; or the like; or lining various bulk material storage areas, such as silos, chutes, bins, storage tanks, or the like.
Such liners most typically take one of two primary forms: (1) mechanically affixed liners and (2) spray-on or dip-applied coating liners. Consistent with the above-described purposes, mechanically affixed liners are often made of metal, plastic, wood, fiberglass, ultra-high molecular weight polyethylene material, and/or other like materials. Most often, such liners are permanently affixed to the substrate material or underlying product through attachment means such as adhesive(s), nails, screws, bolts and nuts, staples, mechanical cleats, magnetic means, or the like. Alternatively, it is common in the industry to apply a semi-permanent or permanent spray-on or dip-applied coating to a base material, in order to obtain a liner with advantageous properties.
For example, commercial liners for bulk storage uses may sometimes involve application of a permanent or semi-permanent, spray-on or dip-applied coating. Some such coatings are surface coatings only; some may chemically bond to the substrate material. Illustratively, in commercial mixers, the liner may be applied to the mixing tank surface; and in storage tank vessels, the liner may be applied to the tank walls. Advantageously, such liners tend to be relatively thin, lightweight, and cost effective to apply. The benefits of such liners to the end-user may include reduced-sticking of a contained material, and easier or more effective cleaning of the container, both of which may further result in a higher yield of the contained or stored product, a more cost effective process, and/or a cleaner or more sanitary process.
Disadvantageously, however, after a period of time, whether soon after heavy use, or after a few years of prolonged use, the spray-on type liner often begins to corrode, chip, spall, or peel away. The only viable solution is to remove and reapply the coating, resulting in downtime and additional expense to the user.
On the other hand, there exist various mechanically affixed liners, and, depending upon the materials used, and upon the intended application, these liners may provide benefits such as resistance to impact (including dent and scratch resistance), and resistance to puncture, corrosion, weather, ultraviolet light, ozone, biocontaminants (such as algae), chemicals, thermal extremes, or the like. Whether alternatively or in conjunction with the above-described benefits, such liners may further provide beneficial characteristics including impermeability, low or high surface friction, elasticity, rigidity, hardness, water tightness, and greater load bearing capacities, strength, toughness, and durability. Accordingly, such liners are often used in bulk storage areas in order to take advantage of one or more of the aforementioned beneficial characteristics, such as ease of cleaning, impermeability, corrosion resistance, impact resistance, and strength.
Presently emerging in the industry are thoughts of using ultra-high molecular weight polyethylene materials and polyurethane materials in liners, due to certain desirable characteristics, including low permeability, high durability and impact resistance, and, depending upon the material and formulation, low or high surface friction characteristics. For example, ultra-high molecular weight polyethylene material exhibits low frictional characteristics and is, therefore, desirable for use in applications requiring a slick, non-stick surface. Polyurethane materials exhibit high durability and resistance, and desirable moldability and shaping characteristics.
Thus, while beneficial and useful characteristics in certain important applications, these very same characteristics create a challenge for use as a removable liner. Specifically, UHMWPE material cannot easily be used as a removable liner. This is because UHMWPE material cannot be conveniently attached to a substrate without damage to the underlying substrate and to the liner, in large part due the physical properties of UHMWPE material. Specifically, and as discussed above, UHMWPE material is a low friction material and, therefore, adhesives will not adhere. Furthermore, thermal welding is difficult/impractical with the current state of manufacturing process technology. Likely for these reasons, there are no known easily removable liners utilizing UHMWPE material.
Specifically, available processes require mechanical attachment to the underlying substrate, often requiring modification of, or permanent structural change to, both the substrate and liner. For example, in the prior art, it is known to use brackets, cleats, and “nuts and bolts” to attach a liner sheet to a substrate material. Specifically, the prior art discloses the use of a protective liner retainer in combination with a panel attachment member to secure the retainer to a cargo panel of a cargo bed or other material handling bin, a liner attachment member with cleats for securing a protective liner to the retainer, and a support member for attaching the liner attachment member to the panel attachment member and for defining the thickness of liner that may be secured by the retainer by separating the panel attachment member and the liner attachment member. It is also contemplated in the prior art to attach brackets to the storage area via magnetizing with continuous use of cleats. However, no specific teaching is made for a removable liner that is bracket and cleat free.
It is apparent in the prior art that use of UHMWPE material as a liner for bulk storage requires substantial modification to the substrate material in order to use. Specifically, to attach the UHMWPE material, the present options in the prior art include drilling of holes, tapping of holes, addition of mechanical elements (such as brackets, cleats, screws, nuts and bolts, and the like) to the substrate material. As a result, the UHMWPE liners are not easily removable, and mere installation results in damage to the liner and/or the substrate. Furthermore, problems with use of the aforementioned connection means includes, corrosion, stress cracks, breakage, catching of stored materials, difficulty in cleaning, cross-contamination of contained product, and the like.
In sum, then, liners in the prior art require an extensive amount of effort to install and remove. Also, due to the means of attachment, damage to the substrate material may occur. This damage includes initial modification of the substrate surface to provide attachment points, with attendant scratching, gouging, holes, rusting, cracking, water penetration and damage, contained product seepage, contamination, draw-down, or the like.
Further disadvantageously, such liners in the prior art are prone to frequent replacement issues. Specifically, when the liners are installed using conventional nut and bolt attachment means, or the like, the liner material experiences an increased level of stress in focused portions of the UHMWPE material, which may result in stress cracking Therefore, there is increased risk that the user will have to constantly replace the liner, resulting in additional and unnecessary costs to the user.
II. Mechanical Screens
The subject matter of the present disclosure is also applicable to a classification of products known in the relevant industry as “mechanical screens” or “screens,” and these terms will be used interchangeably herein. Mechanical screens are typically utilized in an automated or semi-automated process called “mechanical screening” or “screening,” and, again, these terms will be used interchangeably herein. Screens, and associated screening processes, are utilized in a variety of industries, such as, for example, mining, road building, construction, mineral processing, agriculture, pharmaceuticals, food processing, plastics, metal processing, waste separation, and recycling, to name but a few, wherein the screens principally find use within sorting, sifting, and sizing applications.
For purposes of the instant disclosure, mechanical screening may be thought of as a sieving process of an industrial magnitude. Sieving is a technique by which particulates or granules of different sizes may be separated into a “grade” of material defined by particle size. A sieve typically comprises a peripheral frame, within which is affixed or formed a screen or mesh having openings of a desired size and shape, or a plurality of desired sizes and shapes, sufficient to separate either wet or dry particulate or granular materials of a specific size from a material having a distribution of particle sizes. In the relevant industry, this type of sieve device is most often known as a “screen,” and so the terms “screen” or “mechanical screen” will, again, be understood to encompass any sieve or sieve-like device.
Thus, a small sieve might have very small openings which allow only very fine particles to pass through. Coarse particles are retained in the sieve, or are broken up by grinding against the screen openings, or are separated for storage or subsequent processing. Depending upon the types and/or nature of particles or granules to be separated, sieves with different types, sizes, shapes, or other opening characteristics are used. Most often, a plurality of sieves are utilized in sequential, often stacked-in-parallel arrangement, through which a material with a distribution of particle sizes may be passed, the particle sizes being separated from largest to smallest, whereafter particles of a defined size may be conveyed to a post-separation grinder, crusher, mill, hammer, or the like, to further reduce the particle size (often subsequently to be redirected through a secondary screening process); to a storage area; to an intermediary finishing process; or, to a finished product.
Most often, screening machines comprises a drive mechanism that both transports bulk material to the screens and induces motion and/or vibration in order to assist the screening process. The material is received by one or more screens which, most often, rest upon, or within, either a horizontal or inclined decking structure. The screens may be organized in sequential arrangement or, more typically for space-savings and material handling efficiencies, are provided in an inclined, stacked-in-parallel (multi-deck) arrangement.
Screening processes may fail or may be otherwise impeded by a variety of conditions which affect the screen or screens during use and operation. For example, plugging, wear, blinding, breakage or tearing, foreign body contamination, fines or oversize particle contamination, dampening, and/or a variety of other conditions may arise which degrade the screens and, thereby, the screening process. In such circumstances, the affected screen or screens must be repaired, replaced, maintained, and/or otherwise manipulated, in order to remedy the deleterious condition. Such remediation nearly always requires human intervention through hands-on maintenance, restoration, repair, and/or other mitigation of the problematic condition.
Notwithstanding, in many currently available machine designs, it is exceedingly difficult to access the screens for such maintenance-related activities. Even when access is achieved, current means of affixation and/or capture of the screens into the machine deck structure requires the use of wrenches, crowbars, hammers, or the like, in order to dislodge, reinstall, or otherwise maintain the problematic screen or screens. Given that most screening machines have exceedingly small clearance spaces between machine components and/or decks (often <70 cm), access to the screens and support decks, and the use of tools thereupon, is often exceedingly difficult. Further compounding the problematic nature of such maintenance-related activities is that such areas are potentially unsafe, due to the risk of falling materials, with a potential for particulate-related injuries to the eyes or respiratory system, and the risk of impact related injuries to head, neck, shoulders, back, or the like.
Additionally, it will be recognized that there exist many different types, styles, and manufacturers of screening machines, and of the screens utilized therewith. Accordingly, there remains a need for interchangeability and standardization of mechanical screens and their attendant mounting systems utilized in such machines, with concordant flexibility, ease of use, and ease of maintenance thereof. In view of the above discussion, such an improved system may increase workplace safety and reduce the number and/or nature of injuries. Such an improved system may result in cost-effective screen replacement and maintenance processes, including attendant labor savings.
In order to be effective, however, such a system should require no significant changes with regard to tried and true screen materials, and should require no significant redesign of the screens or of the machines that utilize them. Such a system would provide screens that are scaleable in size and/or design, and that would be effective in use and operation, with relatively few modifications or changes to either the basic screen or deck design.
In view of the above discussions with regard to liners and mechanical screens, then, it is apparent that industrially-viable, easily removable mechanical wear elements, such as those preferably taking the form of the aforementioned liner and/or mechanical screening products, have not been contemplated in the prior art, especially with regard to the use of UHMWPE and polyurethane materials, which can be applied to a substrate material without modification of the substrate material. Due to the widespread use of ferrous metals within industrial substrates, there is now presented an opportunity to develop a mechanical wear element having novel means of attachment, while taking advantage of certain desirable, inherent properties of the selected mechanical wear element materials, in order to provide a mechanical wear element that is easily manufactured, easily applied, easily used, easily removed, and easily replaced; all without requiring deleterious modification of the substrate material and, thereby, avoiding or obviating the above-discussed attendant disadvantages of such deleterious attachment methods.
Therefore, what is needed in order to address the above-noted disadvantages and opportunities, but which has not heretofore been available, are novel, removable, magnetically-affixed mechanical wear elements, such as those taking the form of liners and screens, comprising ultra-high molecular weight polyethylene or polyurethane materials, and related processes for producing, installing, and using said magnetic, removable mechanical wear elements. The mechanical wear element of the present invention are preferably configured so that the magnetic attachment means are not easily removed or dislodged from the mechanical wear elements, regardless of liner or screen material choice. It is to such desirable ends that the following developments in the state of the art are presented.